The present invention relates to a gear cutting method which can extensively shorten cutting hours.
There is known a method for cutting inner gears and outer gears in a large ring body having a diameter exceeding 1 m by using a pinion cutter and a hob cutter. According to this method, the objective gear is processed and finished into a gear having a predetermined dimension by incrementally feeding the pinion cutter of the hob cutter through a plurality of cutting processes. It is usual practice with such a conventional method to wait until the ring body cools down to its normal temperature every time each of the cutting processes is effected since its ambient temperature increases by cutting heat with every cut. Only after cooling is the next cutting process resumed; otherwise, the cutting operation is effected while maintaining the work in a constant temperature.
The reason for the above is that if the gear is attempted to be finished by a single cutting process by increasing the feeding amount, the ring body is expanded by cutting heat, which results in adjacent pitch errors, accumulative pitch errors, trace errors, etc. of the gears.
The conventional method requires not only a plurality of cutting processes, but also an extremely long time is required for waiting until the ring body cools down every time each cutting is effected. Accordingly, there exists such a serious problem since it takes about 24 hours to finish a piece of gear.
In order to solve the above problem, there has been proposed a method in which the whole ring body is cooled down during the cutting operation. It is possible to cut down the time required for cutting processes if this method is employed. However, there arise other problems such that it is complicated, time consuming additional work to put the whole ring body in, for example, a water tub for cooling, and to set the whole ring body to a gear planar and remove therefrom.
The present invention is accomplished in order to solve the above-mentioned problems inherent in the prior art.